The theme of a story is usually revealed during which part of the plot?
C. Rising action
Although theme is explored throughout an entire story, a reader can fully grasp a much clearer meaning of everything that was established by the author during the rising action.
In the rising action, all the events and circumstances developed in the story increase the tension of a story. During this moment of the plot, unexpected revelations or incidents take place and that often connect the previous exposition to the overall essential theme.
For example, in Tolkien's The Fellowship of the Ring, at the moment Frodo is given the evil ring to destroy it, the readers understand the story's main theme is the struggle of good vs. evil.
